1. Field of the Invention
The present invention relates to a manufacturing method of a semiconductor device.
2. Description of the Related Art
Semiconductor elements such as transistors using silicon for their semiconductor layers (hereinafter abbreviated as silicon semiconductor elements) have been used for a variety of semiconductor devices and been essential for manufacturing semiconductor devices. To manufacture large-size semiconductor devices, a method in which a material such as glass, which is suitable for increasing in size, is used for substrates and thin-film silicon which can be deposited in a large area is used for semiconductor layers has been widely employed.
In such semiconductor elements using thin-film silicon, the semiconductor layers need to be formed at temperatures less than or equal to the upper temperature limits of their substrates, and thus, amorphous silicon and polysilicon which can be formed at relatively low temperatures have been widely used.
Amorphous silicon has advantages of being able to be deposited in a large area and allowing semiconductor elements having uniform element characteristics to be manufactured by a simple process at relatively low cost; thus, amorphous silicon has been widely used for semiconductor devices with a large area, such as solar batteries. Meanwhile, amorphous silicon has a disadvantage of low electron mobility owing to its amorphous structure which causes a scattering of electrons at grain boundaries.
To make up for the disadvantage, polysilicon, that has a higher mobility realized by irradiating amorphous silicon with laser or the like to be locally dissolved and recrystallized, or by crystallization using a catalytic element, has been widely used in semiconductor devices such as liquid crystal displays in which both large area and high carrier mobility need to be achieved.
In addition, in recent years, oxide semiconductors that are metal oxides having semiconductor characteristics have attracted attention as novel semiconductor layer materials having high mobility, which is an advantage of polysilicon, and uniform element characteristics, which are an advantage of amorphous silicon.
As semiconductor devices such as transistors using oxide semiconductors as their semiconductor layers (hereinafter abbreviated as oxide semiconductor devices), for example, as in Patent Document 1, a thin film transistor manufactured using tin oxide, indium oxide, zinc oxide, or the like has been proposed.